The present invention relates to a system for decreasing the amount of fuel injection at and/or immediately after an engine start according to the state of an engine at which the engine is stopped preceding the present engine start, whereby preventing a spark plug malfunction by excessively injected fuel.
It is known that a required amount fuel injection at an engine start is affected by external circumstances such as ambient air temperature and fuel temperature.
In a conventional engine a required amount of fuel injection at an engine start is commonly determined only by coolant temperature, that is to say, at a cold start of an engine when the coolant temperature is low, the amount of fuel injection at an engine start is increased because the fuel stuck to an inner wall of the intake manifold or other portions of the intake system is hard to vaporize.
On the other hand, at a hot start where the coolant temperature is relatively high, the amount of fuel injection at an engine start is determined in a decreased value because vaporization of fuel becomes high in the intake system.
In this type of control system for a conventional engine, once an ignition key switch is turned off, the data memorized in a RAM (RANDOM ACCESS MEMORY) are erased, so that the amount of fuel injection at a re-starting of engine has to be reestablished according to the coolant temperature at the re-starting.
Therefore, for example, in such a case where frequent cold starts are conducted with a state of incomplete warming up, air-fuel mixture of an engine becomes ever-rich because of excessive fuel and thus a fouling is caused at the spark plugs. Once the fouling is caused, it becomes very difficult to re-start the engine.
Japanese patent application laid open No. 1989-8330 discloses a technology to determine a start increment by reading the data stored in a ROM(READ ONLY MEMORY) for residual fuel amounts sticking on an inner wall of the intake manifold or the intake ports according to the engine operating condition immediately before an engine stall occurrence, then correcting these fuel amounts data by a re-start correction coefficient which is determined on a map indicating a relationship between the coolant temperature and the time from an engine stall occurrence to a next cranking start and then subtracting this correction coefficient from the fuel injection amount at the engine start which is calculated according to the engine operating conditions such as coolant temperature and cranking revolution numbers.
According to this prior art, the amount of fuel sticking on an inner wall of intake manifold is determined based on the engine operating conditions immediately before an engine stall occurrence.
However, in this prior art, once the ignition key switch is turned off after an engine stall occurrence, it is very difficult to re-start the engine because the data concerning the sticking fuel amount and the time from engine stall to cranking start are erased from the RAM and an appropriate fuel amount at an engine start is no longer provided. Further in this system, in order to obtain a good re-starting performance, a timer must be continued to be operated after an ignition key switch is turned off, so that electrical power is consumed so much.